Add M3U playlist / XMLTV export for external IPTV players

[selcukkirtas]

What

Exposes the live channels a neTV user can access as an Xtream-style playlist, so external IPTV players (TiviMate, IPTV Smarters, VLC, etc.) can use neTV as a source:

• GET /get.php?username=U&password=P → M3U playlist (m3u_plus attributes: tvg-id, tvg-logo, group-title)
• GET /xmltv.php?username=U&password=P → XMLTV guide generated from the local EPG database
• GET /live/U/P/{stream_id}.ts → channel playback

Why

neTV's web UI is great on desktops and TVs with a browser, but many households also have devices where a native IPTV player app is the better (or only) option. This lets one neTV instance serve both, with the same user accounts and channel restrictions.

How

• Two playback modes (admin-selectable in Settings → M3U Export):
  • redirect (default): 302 to the provider URL — zero server bandwidth.
  • proxy: bytes flow through neTV — hides the provider URL/credentials from clients and enforces per-user + per-source stream limits. HLS direct URLs always redirect (proxying would require rewriting segment URLs).
• Auth integration: credentials in the URL are the normal neTV accounts. Per-user unavailable_groups filtering applies to both the playlist and playback; failed attempts feed the existing login rate limiter. PBKDF2 verification results are cached in memory (5 min TTL, invalidated on password change/user delete) so channel zapping stays fast on small ARM boards.
• Off by default; enabled via a new Settings section that also displays the player URLs.

New logic lives in m3u_export.py with routes in main.py, following the existing ffmpeg_session.py module/route split.

Testing

• 31 new tests in m3u_export_test.py (credential caching, playlist/XMLTV generation, group restrictions, stream limits, and route-level tests incl. redirect/proxy modes and rate limiting).
• Full suite passes: 412 tests. ruff and basedpyright clean.

🤖 Generated with Claude Code